An investigation of antigens specific to six major species of mycobacteria is proposed with the objectives of identifying species specific mycobacterial antigens, characterizing them, isolating them, and preparing monospecific antisera to them. If these objectives can be accomplished, then improved tuberculin skin testing reagents, improved mycobacterial taxonomy, and improved laboratory methods for the identification of mycobacteria in clinical specimens may result. Mycobacterial culture filtrates will be prepared and goats will be immunized to give polyvalent reference antisera to each species. Using these sera, apparently specific antigens will be selected and isolated by combining physicochemical fractionation procedures with absorption by nonspecific immunoglobulin and lectin affinity absorbents. Using antigens thus isolated, monospecific antisera will be raised in goats and subsequently used to prepare immunoabsorbents for the affinity chromatography preparation of additional supplies of purified antigens. The same monospecific sera will be used as reagent antisera. Purified antigens will be tested for skin test specificity in sensitized guinea pigs. Monospecific antisera will be used in conventional bacterial agglutination methods of mycobacterial serotyping and will also be used in previously untried methods of sero-typing, including fluorescent antibody staining. This approach will also be used in an attempt to identify these organisms in clinical specimens.